The big picture: Plants evolved from green algae
- Cyanobacteria & protist made landfall ~1.2 bya
- plants, fungi and animals ~500 mya
- first forests 385 mya
- Plants evolved from green algae
- Several key ‘shared traits’
- WHAT DO YOU THINK THEY ARE?
- Plants support all life on earth
- Oxygen to breath
- food to eat
- new habitats

Protists that share traits with plants
- Dinoflagellates - unicellular aquatic
- some are photosynthetic
- haploid dominate life cycle
- Brown Algae - large multicellular aquatic
- AoG life cycle
- identical haploid and diploid life cycle
- photosynthetic
- Diatoms - unicellular aquatic
- all are photosynthetic
- diploid dominated life cycle

Not ancestral to plants!

Green Algae (Oedogonium)
- Sister group to land plants
- all are photosynthetic
- marine and freshwater
- single and multi-cellular
- broad, thick filaments
- some have AoG
- evolved around ~750mya
- Reproductive features:
- Oogonia = egg containing cell
- Antheridium = sperm containing cell


Molecular evidence points at charophytes as plant ancestors


Charophytes (freshwater green algae)
- Transition from water to land starts with Charophytes
- freshwater habitats may have dried
- a population eventually lived above water line
- More shared traits with land plants:
- circular protein rings in plasma membrane
- make cellulose fibers in cell wall
- swimming sperm with similar structure
- phragmoplast (something with cell division)
- ROS genes

Living on Land: The Wild Wild West

Land plants are a monophyletic group

Shared Traits define plant evolution


Multi-cellular, Dependent embryos (placental transfer)

Waxy cuticle and stomata


Multi-cellular Gametangia

Photosynthesis with unique pigments (chlorophyll A & B)

Unique cell walls
- Cells walls made of cellulose
- Pectin to fortify cell walls
- Produce cells walls in unique way

Alternation of generations

First plant group: non-vascular bryophytes (mosses)
- Mosses, hornworts and liverworts
- Fossils of bryophyte spores ~470mya
- Non-vascular; ground hugging carpets
- bodies to thin to support height growth
- Have a rhizoid but not a root
- anchors plant
- does not uptake water


Bryophytes have gametophyte dominated life cycle
